1. Field of the Invention
The present invention relates to a hand tool having an adjustable head with joint lock mechanism, especially a hand tool with a head of adjustable angles and easier, more secure positioning. The present application claims priority based on ROC (Taiwan) Patent Application No. 093208736.
2. Description of the Related Art
Conventional hand tools with an adjustable head, for example, as disclosed in TW421111, corresponding to U.S. Pat. No. 6,295,898, and TW488349, comprise a head and a handle. The head has a convex portion which can be pivotally coupled to a concave portion of the handle. Teeth are disposed along the surface of the convex portion to engage a ball received in an aperture formed in an inner wall of the concave portion. A stop member is disposed between the head and the handle. A positioning portion is formed at a rear side of the stop member and is coupled to a front end of the handle. A toothed portion formed at a front side of the stop member is engageable with a toothed surface portion formed along the surface of one side of the convex portion. When the stop member is slid to a predetermined position, the adjustment and positioning of the head at a certain angle can be more securely and conveniently done. However, with this kind of wrench, the ball is of a circular shape and cannot ensure secure engagement, and similar to the configuration of a ball and a toothed portion of a convex portion, the toothed portion of the stop member and the toothed surface portion of the handle may be worn out after use for a long period, which can therefore cause inconvenience when in use and reduce the life time of the hand tool.
TW478444; has disclosed a wrench wherein a through hole is formed in the centre of a shaft and threads are formed on a wall of the through hole at a bottom of the shaft to receive an operation rod. A handle is mounted at a bottom end of the operation rod and rotates synchronously with the operation rod. A concave portion formed at a top end of the shaft is coupled to a head and secured by a screw. A retainer is received in the through hole of the shaft with its one end coupled to the top end of the operation rod and an arc shaped concave portion formed on the other end. A rotatable worm supported by a retainer is disposed in the concave portion of the shaft and a groove fitted with a clip is formed at a protrusion of the worm at one end. A worm gear is disposed at an extension end of the head and engages the worm. The other end of the worm is coupled to a pivotal block and a crane to actuate the worm gear and the worm such that the head can be rotated at any angle. Again, with this configuration, the worm and the worm gear may be worn out after use for a long period, which causes the local structure to be loose and unable to be positioned properly. In addition, it is likely that the clip, operation rod, the retainer or the pivotal block and the crane might become loose and make the wrench un-useable.
From the above, it is necessary for the industry to provide a hand tool having an adjustable head with joint lock mechanism, which offers convenient and secure angle adjustment and positioning and can overcome the defects mentioned in the prior art.